Conservative leadership favourite Boris Johnson ruled himself out of the contest. The move comes after justice secretary Michael Gove, a fellow Vote Leave campaigner, made a surprise bid to become David Cameron's successor as prime minister.
Here is the conclusion of the former London Mayor's speech in full:
"That is the agenda for the next prime minister of this country.
"Well, I must tell you, my friends, you who have waited faithfully for the punchline of this speech, that having consulted colleagues and in view of the circumstances in parliament, I have concluded that person cannot be me.
"My role will be to give every possible support to the next Conservative administration to make sure that we properly fulfill the mandate of the people that was delivered at the referendum and to champion the agenda that I believe in, to stick up for the forgotten people of this country.
"And, if we do so, if we invest in our children and improve their life chances, if we continue to fuel the engines of social mobility, if we build on the great reforming legacy of David Cameron, if we invest in our infrastructure and we follow a sensible, one nation Conservative approach that is simultaneously tax-cutting and pro-enterprise, then I believe that this country can win and be better and more wonderful and, yes, greater than ever before."